In the optical arts various systems for correcting optical aberrations shown by the human eye are very well known. However, such systems generally comprise the superposition, to the defective eyes, of an artificial lens or of a series of artificial lenses suitably designed and calculated to the effect that, by means of the joint and complementary action of said lenses with the defective eye, the defects presented by the latter be corrected.
Thus, according to the traditional optical arts, spherical aberrations are corrected by means of the addition of various elements that jointly refract the light such that the same will be directed in the adequate directions in order to avoid sphericity of the images projected or observed through the eyes.
Other type of aberrations, known as astigmatism, farsightedness or presbyopsia, myopic astigmatism and the like, also constituting common diseases of the human eye, are corrected in accordance with the prior art, by means of lenses suitably designed to compensate the deficient refraction of the light rays produced by defects either in the cornea or in the crystalline of the eye.
However, the above mentioned technique of adding correcting lenses is highly costly and requires very accurate calculations, whereby the correcting lenses normally result of a high price.
One other method of partially correcting optical aberrations are the non-refracting devices such as the so called stenopeic spectacles which have been known as a visual aid from early times. For instance, in the text book System of Ophthalmology, by Sir Steward Duke-Elder and David Abrams, edited by Sir Stewart Duke-Elder, Volume V, pages 794 et seq, it is very clearly mentioned that said stenopeic spectacles were advocated and their optical principles explained by Daza de Valdes in 1623, and were first employed clinically by the French Ophthalmologists Serre in 1857 and Frans Donders in 1864. However, as also clearly stated in said text book, the main disadvantage of a stenopeic hole is that it provides a very small visual field and, since it does not move with the eye, it is of little advantage to the wearer when walking about. It is also mentioned in said text book that when it is required for general purposes a disc composed of several such openings bored in a sheet of opaque material may prove "better than nothing", which means that said stenopeic spectacles have proven to be highly inefficient articles and, as is also well known and mentioned and described in many optics books, a stenopeic hole has as its sole purpose to avoid the entrance into the defective eye of the diffraction circles that generally accompany pure light rays, whereby said stenopeic holes must be obviously of circular shape, and as Duke-Elder et al very clearly mention in their text book, in order to be effective, the multiplicity of stenopeic holes provided in spectacles, must be spaced in about 4 mm. between each other, and must have a size of about 1.5 mm. for distant vision and 0.3 mm. for near vision.
The fact that the stenopeic holes have as their only purpose to prevent the entrance of the diffraction circles, whereby their form must be obviously circular, and the fact that the spacement thereof must be relatively large in stenopeic spectacles, render said stenopeic spectacles highly impractical devices for general use, inasmuch as the effort of the wearer is not compensated by the benefit produced by the improvement of the image perception, and thus said stenopeic spectacles have not gained any acceptance among the general public, regardless of the fact that many persons may be in real need of something more than mere spectacles or mere contact lenses to improve their vision. The problems encountered with the decrease in the perception of light intensity and vision angle with the stenopeic holes, is of considerable importance and has been determinant of the lack of acceptance for these devices among the public.
The stenopeic spectacles were improved by Guthrie, who provided a surface covered by stenopeic holes of the size and with the spacement mentioned above, with an additional centrally arranged so called stenopeic slit, in order to increase vision at least when reading, but the stenopeic slit may be regarded as highly inefficient for many particular purposes, and more particularly when the defects in the eye to which the said stenopeic slit is superposed, include aberrations of the spherical type and more particularly astigmatism.
In Mexican Patent No. 132,553 patented Feb. 10, 1976 to the same applicant hereof, an optical grid is described for causing interference of light rays and which to a great extent remedied the defects of the devices of the above described techniques, including the stenopeic spectacles.
Said grids were designed for application to spectacles and comprised an undetermined number of square openings, said grids being either flat or concave to be adapted to the rings of ophthalmic frames for spectacles with conventional glasses and/or in substitution thereof.
Even when the optical grid of Mexican Patent No. 132,553 is very efficient to correct optical aberrations particularly caused by the excess of luminosity, by means of a process of light interference effected through the plurality of square holes that it contains, the said grid does not provide any usefulness in the correction of optical aberrations of other types and, of course, the said optical grid is mainly based in the decrease of the light intensity by means of said interference, thus causing obscurity or lower intensity of the light detected, with a better perception of the images. However, the considerable decrease of luminosity produced by the grids of Mexican Patent No. 132,553 is in itself an inconvenience, in view of the fact that particularly in dark places or in the twilight time of the day, as well as in the darkness of the night, the use of said grids causes a loss of visual intensity which is not compensated by the improvement of the image perception, and this may cause the loss of perception of many dark objects.
The principle of providing square holes uniformly spaced from each other, however, as described in said Mexican Patent No. 132,553, for the first time changes the concept of using stenopeic holes for trying to improve visual perception, and may be regarded as a considerable improvement in the art of correcting optical aberrations of lenses. However, this grid was very primitive and may be regarded as a first effort of applicant to provide a practical device that could be used in substitution of glasses for spectacles, without the loss of light intensity and however with a high improvement in the image perception and an absolute correction of optical aberrations as will be described in the instant application.
U.S. Pat. No. 4,452,516, patented June 5, 1984, to the same applicant hereof, describes for the first time what might be regarded as the definite solution to the problem of correcting optical aberrations suffered by the eyes of the human beings without the need of using refractive lenses or the like. This patent describes an optical grid that may be used for the manufacture of spectacles, and which comprises two series of bars of triangular cross section, arranged parallel to each other and with each series perpendicularly arranged with respect to the other series in order to form a grid leaving square free spaces therein, the apexes of said bars being directed toward the outer face of the grid, on which the light falls and the bases of said bars being directed towards the inner face of the grid which is directly confronted to the eyes which defects are desired to correct, said square free spaces constituting openings of a square frustopyramidal shape, the larger base of which is at the inner face of the grid, the area of said larger base of the openings being in a ratio of from about 36:1 to 2.25:1 with respect to the area of the smaller base, the total area of the smaller base of each one of said square openings being of from about 0.04 to about 4 mm.sup.2, and the width of said bars being of about 1 mm.
Although the optical grids and spectacles of U.S. Pat. No. 4,452,516 may be regarded as absolutely efficient to correct optical defects of the human eye, the spectacles of said patent were restricted to be used only in lieu of or in addition to prescription lenses, but did not permit the sportsmen to make use thereof particularly for swimming or diving or the like, because the effect of the water within which said spectacles were submerged, is to fill the square openings of the grid, thus completely impairing the vision of the wearers when leaving the water pool.